إِنَّ ٱلَّذِينَ يَأْكُلُونَ أَمْوَٰلَ ٱلْيَتَٰمَىٰ ظُلْمًا إِنَّمَا يَأْكُلُونَ فِى بُطُونِهِمْ نَارًۭا ۖ وَسَيَصْلَوْنَ سَعِيرًۭا ﴿١٠﴾
侵吞孤儿的财产的人，只是把火吞在自己的肚腹里，他们将入烈火之中。
Haram Money & business
Is taking an orphan's wealth haram?
Short answer
Yes. Allah warns that those who consume the wealth of orphans unjustly only consume fire into their bellies (4:10). The Prophet ﷺ counted it among the seven great destructive sins.
Evidence
Quran
وَلَا تَقْرَبُوا۟ مَالَ ٱلْيَتِيمِ إِلَّا بِٱلَّتِى هِىَ أَحْسَنُ حَتَّىٰ يَبْلُغَ أَشُدَّهُۥ ۖ وَأَوْفُوا۟ ٱلْكَيْلَ وَٱلْمِيزَانَ بِٱلْقِسْطِ ۖ لَا نُكَلِّفُ نَفْسًا إِلَّا وُسْعَهَا ۖ وَإِذَا قُلْتُمْ فَٱعْدِلُوا۟ وَلَوْ كَانَ ذَا قُرْبَىٰ ۖ وَبِعَهْدِ ٱللَّهِ أَوْفُوا۟ ۚ ذَٰلِكُمْ وَصَّىٰكُم بِهِۦ لَعَلَّكُمْ تَذَكَّرُونَ ﴿١٥٢﴾
你们不要临近孤儿的财产，除非依照最优良的方式，直到他成年；你们当用充足的斗和公平的秤，我只依各人的能力而加以责成。当你们说话的时候，你们应当公平，即使你们所代证的是你们的亲戚；你们当履行真主的盟约。他将这些事嘱咐你们，以便你们觉悟。
Hadith
Sahih al-Bukhari 2766
Narrated Abu Huraira:The Prophet (ﷺ) said, "Avoid the seven great destructive sins." The people enquired, "O Allah's Messenger (ﷺ)! What are they?" He said, "To join others in worship along with Allah, to practice sorcery, to kill the life which Allah has forbidden except for a just cause, (according to Islamic law), to eat up Riba (usury), to eat up an orphan's wealth, to give back to the enemy and fleeing from the battlefield at the time of fighting, and to accuse, chaste women, who never even think of anything touching chastity and are good believers
Arabic text (with chain of narrators)
حَدَّثَنَا عَبْدُ الْعَزِيزِ بْنُ عَبْدِ اللَّهِ، قَالَ حَدَّثَنِي سُلَيْمَانُ بْنُ بِلاَلٍ، عَنْ ثَوْرِ بْنِ زَيْدٍ الْمَدَنِيِّ، عَنْ أَبِي الْغَيْثِ، عَنْ أَبِي هُرَيْرَةَ ـ رضى الله عنه ـ عَنِ النَّبِيِّ صلى الله عليه وسلم قَالَ " اجْتَنِبُوا السَّبْعَ الْمُوبِقَاتِ ". قَالُوا يَا رَسُولَ اللَّهِ، وَمَا هُنَّ قَالَ " الشِّرْكُ بِاللَّهِ، وَالسِّحْرُ، وَقَتْلُ النَّفْسِ الَّتِي حَرَّمَ اللَّهُ إِلاَّ بِالْحَقِّ، وَأَكْلُ الرِّبَا، وَأَكْلُ مَالِ الْيَتِيمِ، وَالتَّوَلِّي يَوْمَ الزَّحْفِ، وَقَذْفُ الْمُحْصَنَاتِ الْمُؤْمِنَاتِ الْغَافِلاَتِ ".
This is general information, not a fatwa. For your own situation, ask a qualified scholar.
Questions about halal and haram
Is taking an orphan's wealth haram?
Yes. Allah warns that those who consume the wealth of orphans unjustly only consume fire into their bellies (4:10). The Prophet ﷺ counted it among the seven great destructive sins.